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钠钾泵工作原理介绍

(2009-05-16 08:07:18)
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杂谈

    Na+-K+泵 ——实际上就是Na+-K+ATP酶,存在于动,植物细胞质膜上,它有大小两个亚基,大亚基催化ATP水解,小亚基是一个糖蛋白.Na+-K+ATP酶通过磷酸化和去磷酸化过程发生构象的变化,导致与Na+,K+的亲和力发生变化。大亚基以亲Na+态结合Na+后,触发水解ATP。每水解一个ATP释放的能量输送3个Na+到胞外,同时摄取2个K+入胞,造成跨膜梯度和电位差,这对神经冲动传导尤其重要,Na+-K+泵造成的膜电位差约占整个神经膜电压的80%.若将纯化的Na+-K+泵装配在红细胞膜囊泡(血影)上,人为地增大膜两边的Na+,K+梯度到一定程度,当梯度所持有的能量大于ATP水解的化学能时,Na+,K+会反向顺浓差流过Na+-K+泵,同时合成ATP。
  钠钾水泵的一个特性是他对离子的转运循环依赖自磷酸化过程,ATP上的一个磷酸基团转移到钠钾泵的一个天冬氨酸残基上,导致构象的变化。通过自磷酸化来转运离子的离子泵就叫做P-type,与之相类似的还有钙泵和质子泵。它们组成了功能与结构相似的一个蛋白质家族。
  Na+-K+泵作用是:①维持细胞的渗透性,保持细胞的体积;②维持低Na+高K+的细胞内环境,维持细胞的静息电位。
  乌本苷(ouabain),地高辛(digoxin)等强心剂能抑制心肌细胞Na+-K+泵的活性;从而降低钠钙交换器效率,使内流钙离子增多,加强心肌收缩,因而具有强心作用。

Na +-K + pump - in fact, Na +-K + ATP enzyme, exists in animals and plants cytoplasmic membrane, it has the size of the two subunits, the catalytic subunit of ATP hydrolysis, the small subunit is a glycoprotein. Na + -K + ATP enzyme through phosphorylation and phosphorylation of the process to conformational changes occur, leading to Na +, K + affinity change. Large subunit of Na + in the pro-state binding Na +, the trigger hydrolysis of ATP. Each of ATP hydrolysis to release the energy of a transfer to the three extracellular Na +, and two K + uptake into the cell, resulting in transmembrane gradient and potential difference, which is particularly important in nerve impulse conduction, Na +-K + pump caused by membrane potential difference of the nerve membrane voltage about 80%. If the purified Na +-K + pump assembly in the red cell membrane vesicles (blood film), the membrane on both sides of artificially increasing the Na +, K + gradient to a certain extent, When the gradient is greater than the energy held by the chemical energy of ATP hydrolysis when, Na +, K + concentration difference will reverse the flow Shun Na +-K + pump, while synthesis of ATP.
A sodium-potassium pump characteristics was his transfer of ions from the cycle of phosphorylation-dependent process, ATP a phosphate group transferred to a sodium-potassium pump at Asp residues, resulting in conformational changes. To the adoption of self-phosphorylation of the ion pump ion transporter called P-type, which are similar to calcium pump and proton pump. They formed a similar function and structure of a protein family.
Na +-K + pump function is: ① to maintain the permeability of cells to maintain cell volume; ② maintain a low Na + high K + within the cell environment, the maintenance of cell resting potential.
Ubundu glycoside (ouabain), digoxin (digoxin) and other cardiac myocytes can inhibit Na +-K + pump activity; thereby reducing the efficiency of sodium-calcium exchanger, so that increased calcium influx to enhance myocardial contractility, which has a strong heart role.
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